Common Degenerative Eye Disease May Be Triggered By Tiny Mineral Deposits

A new research article that appeared in the latest issue of the Proceedings of the National Academy of Sciences reveals that the scientists at the University Of Maryland School Of Medicine (UM SOM) have discovered that tiny lumps of calcium phosphate may significantly contribute to the triggering of age-related macular degeneration (AMD), a degenerative diseases of the eyes that can cause severe vision loss and blindness and which affects more than 10 million Americans. It is for the first time that the role of these mineral deposits has been found to be of significance in this disease.

For this study, retinal samples from a group of elderly patients, some of whom had AMD were studied by the researchers which included Biochemist Richard Thompson, PhD, Imre Lengyel, PhD – his colleague from University College, London, and a multidisciplinary international team. Their study revealed that the AMD samples contained hydroxyapatite, or HAP which are tiny spherules of a mineralized calcium phosphate. HAP is common in the body  it is what comprises the hard part of bones and teeth. However, never before it had been identified in that specific part of the eye.

It was known that AMD is characterized with the buildup of fatty protein deposits in the retina; however how they came about was not fully understood. When a significant deposit builds up in the eyes, it blocks the flow of nutrients into the light-sensitive portion of the eye and also hinders the way waste is flushed out of the eyes. In the study, Thompson and Lengyel discovered that the deposits seem to form around the tiny bits of HAP. Once these bits appear, the fatty protein material gets deposited around it and over years, these globules build up.

Prof. Thompson, who is an associate professor of biochemistry and molecular biology at the school, remarked that initially they had no idea about HAP being involved in the process. They made the discovery about its possible role by examining tissue samples from patients using X-ray diffraction and fluorescent staining chemicals.

AMD is so named because it affects the macula  which is the central area of the retina. This part of the eye is responsible for the sharp, direct vision necessary for reading and driving. AMD is typically found to affect older people  more than 11 percent of Americans over the age of 80 have AMD, and about 30 % people above the age of 75 are at the risk of getting advanced AMD. It affects tens of millions people worldwide and is the most common cause of blindness in older people in developed countries. Other factors that can increase the risk of AMD include smoking, some chronic infections, and chronic inflammatory diseases such as diabetes.

There is no cure for AMD. However, sometimes the damage can be slowed or halted by injections of medicines which stop the growth of the deposits. The cost of AMD is estimated at more than $340 billion.

Thompson and Lengyel are hopeful that the presence of HAP can be used as an early warning signal for AMD risk and that it can aid early intervention before patients have suffered irreversible vision loss. They are of the opinion that eventually it may be possible to devise methods that can reduce HAP deposits or limit the growth and progression of the disease.

This research have provided new insight into the deep mechanisms of this disease, and in doing so, new avenues of research have been created which has the potential to help millions of people around the world.